Recently, researches and development of various electronic paper displays have been in progress and, thus, a commercial electronic paper becomes available.
There are some representative examples of an electronic paper display as follows: (1) an electrophoretic type (E-Ink, SiPix) in which electrically charged pigment particles confined in a microcapsule or not are mixed with oil and move in response to application of an electric field; (2) a twist ball type (Gyricon media) in which spherical particles formed of upper and lower hemispheres having opposite charges and different colors are rotated by an electric field; (3) a QR-LPD (Quick Response-Liquid Powder Display) type (Bridgestone) in which electrically charged liquid powder is operated under dry circumstances; and (4) a cholesteric liquid crystal display type (Kent Display) using a selective reflection property of cholesteric liquid crystal molecules.
Among them, the electrophoretic type is the most typical type of an electronic paper display. Particles used in a conventional electronic paper display such as an electrophoretic display have permanent electric charges. However, the particles having permanent electric charges may be disadvantageous in that they require a high driving voltage and they have a low response speed, and they have difficulty in expressing gradations. Further, a color filter is needed to express colors.